core/thisself.cpp

The following code example is taken from the book
C++23 - The Complete Guide by Nicolai M. Josuttis, Leanpub, 2026
The code is licensed under a Creative Commons Attribution 4.0 International License.

---

// raw code

#include <iostream>

class Base {
public:
  // member function with *this:
  void mem() {
    if constexpr (std::same_as<decltype(this), Base*>) {
      std::cout << "Base::mem() compiles for *this of type 'Base'\n";  
    }
    else {
      std::cout << "Base::mem() compiles for *this of a DERIVED type\n";
    }
  }

  // member function with deduced object parameter:
  void ded(this auto& self) {
    if constexpr (std::same_as<std::remove_cvref_t<decltype(self)>, Base>) {
      std::cout << "Base::ded() compiles for self  of 'Base' type\n";  
    }
    else {
      std::cout << "Base::ded() compiles for self  of a DERIVED type\n";
    }
  }
};

class Der : public Base {
};

int main()
{
  Der d;
  d.mem();   // call member function with implicit object *this
  d.ded();   // call member function with explicit object parameter
}